Dental adhesive composition

ABSTRACT

This invention discloses a dental adhesive composition comprising (A) a polymerizable monomer comprising an acidic-group containing polymerizable monomer such as 11-methacryloyloxy-1,1-undecane dicarboxylic acid, (B) a mixed filler of a spherical filler substantially consisting of a non-crosslinking polymethyl methacrylate and a spherical filler substantially consisting of a non-crosslinking polyethyl methacrylate; and (C) a polymerization initiator; and a dental adhesive kit comprising the above dental adhesive composition in combination with a dental primer comprising (D) an acidic-group containing polymerizable monomer, (E) an aryl borate, (F) an organosulfinic acid salt and (G) water. The dental adhesive composition exhibits good operability and improved adhesion performance.

FIELD OF THE INVENTION

This invention relates to a dental adhesive composition, as well as adental adhesive kit consisting of a combination of the dental adhesivecomposition and a dental primer composition.

DESCRIPTION OF THE PRIOR ART

In the field of dental treatment, a damaged tooth due to caries or anaccident must be firmly cemented with a restorative material for thetooth including a crown restorative material made by composite resins,metals and ceramics, and a variety of adhesive compositions have beensuggested for such cementing.

Among these adhesive compositions, adhesive resin cements have beenwidely used because they can firmly cement a metal or ceramic prosthesiswith a tooth. An adhesive resin cement essentially consists of a monomercomponent, a filler component and a polymerization initiator. It isbelieved that an adhesive resin cement containing a non-crosslinkingresin filler (non-crosslinking polymer filler) as a filler componentgives a cured resin cement exhibiting higher toughness than an adhesiveresin cement comprising a crosslinking resin filler or inorganic fillerand is adequately resistant to external stress applied to a prosthesiscemented with a tooth to prevent the prosthesis from being easilydetached from the tooth. Known adhesive resin cements comprising anon-crosslinking resin filler (hereinafter, referred to as aresin-filler resin cement) include resin cements comprisingtributylboran or its partially oxidized (TBBO) as a polymerizationinitiator and a non-crosslinking polymethyl methacrylate filler as anon-crosslinking polymer filler.

Although such a resin-filler adhesive resin cement advantageouslyexhibits higher adhesiveness, it has been indicated that it has thefollowing problems in terms of operability in use. Specifically, theabove polymerization initiator used in the resin cement is chemicallyunstable, so that it must be packed separately from the othercomponents. Furthermore, the non-crosslinking polymer filler and themonomer must be also separately packed for preventing thenon-crosslinking polymer filler from being dissolved. Thus, in the resincement, the polymer filler, the monomer liquid and the polymerizationinitiator solution must be packed separately from each other, i.e., athree-packet system. When using the resin cement, given amounts of themonomer liquid and the polymerization initiator solution are mixed, andthen a given amount of the polymer filler is added. This process istroublesome.

When using the resin cement, the three components can be mixed torapidly increase a viscosity and thus to reduce a time for applying themixture to a tooth surface and a crown restorative material(hereinafter, referred to as a “working time” or “operable time”).Higher technique which ensures rapid and firm cementing is, thereforerequired for achieving desired adhesive strength using the resin cement.When using the polymerization initiator, it takes a longer time untilthe resin cement is adequately cured to exhibit desired adhesiveness.There is thus a problem that a desired adhesive strength cannot beachieved if a strong force is applied after cementing a prosthesis onthe tooth surface and before completion of curing of the resin cement.

There have been no known resin-filler resin cements which cansufficiently endure severe environmental conditions, i.e., in the mouth,to provide good adhesiveness; have a satisfactory working time and anappropriate curing time; and exhibit improved operability.

SUMMARY OF THE INVENTION

An objective of this invention is to provide a resin-filler resin cementmeeting the above requirements.

The above problem in terms of packaging depends on stability of apolymerization initiator used. A curing time basically depends on acombination of a polymerization initiator and a monomer. These problemscould be, therefore, solved by employing a stable polymerizationinitiator and a polymerization initiator-monomer system which can bequickly cured and exhibits higher adhesive ability. Actually, many suchinitiator-monomer systems have been found for a dental adhesivecomposition other than a resin-filler resin cement and have beenpractically used. The above two problems could be, therefore, solved byemploying such a well-known monomer-initiator system.

However, a resin-filler resin cement contains a non-crosslinking polymerfiller as a constituent. Thus, it is inevitable that on mixing a polymerfiller with a monomer in use, expansion or dissolution of the polymerfiller leads to increase in a viscosity of the mixture. It can be thussaid that the above problem in terms of a working time is inherent to aresin-filler resin cement. Furthermore, a working time may varysignificantly depending on a combination of a non-crosslinking polymerfiller and a monomer. A working time might be increased by replacing oneor both of these components. However, since replacing a monomer maysubstantially affect, e. g., an adhesive strength, it cannot be easilyapplied.

We thus considered the problem of a working time as a common problem fora dental adhesive composition comprising a non-crosslinking polymerfiller and a monomer rather than that for a resin-filler resin cementalone. We have, therefore, attempted to solve the problem of a workingtime by first selecting an initiator-monomer system employed in a dentaladhesive composition other than the above resin-filler resin cement andnext developing a non-crosslinking polymer filler providing a suitableworking time when being mixed with the initiator-monomer system.

It is well-known that a working time depends on a shape and a particlesize of a non-crosslinking polymer filler. Specifically, a working timetends to be reduced by using an irregular form non-crosslinkingpolymethyl methacrylate filler as a component of a resin cement while ittends to be increased by using a spherical polymethyl methacrylatefiller (Shika Zairyo-Kikai, Vol. 18, No.5, 347-351, 1999). It is alsoknown that by controlling a particle size or particle size and surfaceroughness of an irregular form non-crosslinking polymethyl methacrylatefiller can increase a working time to some extent (Shika Zairyo-Kikai,Vol. 19, No.1, 92-101, 2000 and JP-A 2000-53727). When using such afiller to adjust a working time, a curing time of a resin cement may beincreased or an elongation of working time may not be sufficient. Theabove problem cannot be solved only by optimizing a shape or particlesize of a filler.

Under such a situation, we have investigated not only a shape and aparticle size of a non-crosslinking polymer filler but also its materialquality. We have consequently found that a resin cement can beformulated using a mixture of a non-crosslinking polymethyl methacrylatespherical filler and a non-crosslinking polyethyl methacrylate sphericalfiller to increase a working time of the resin cement without adverselyaffecting a curing time or adhesive strength, achieving this invention.

This invention provides a dental adhesive composition comprising (A) apolymerizable monomer comprising an acidic-group containingpolymerizable monomer; (B) a spherical filler substantially consistingof a non-crosslinking polymethyl methacrylate and a spherical fillersubstantially consisting of a non-crosslinking polyethyl methacrylate;and (C) a polymerization initiator.

Because a dental adhesive composition of this invention comprises anon-crosslinking polymer filler as a filler component, it can provide acured product exhibiting higher toughness than that from a dentaladhesive composition comprising a crosslinking filler or inorganicfiller. Thus, it can adequately endure a stress applied to a prosthesiswhile maintaining the property in a conventional resin-filler resincement that a cemented prosthesis is resistant to detachment. It canprovide a higher adhesive strength, gives a shorter time to a properviscosity, and gives an appropriately long working time of 40 to 150sec, resulting in good operability. Furthermore, a curing time is asshort as 5 min or less, the dental adhesive composition of thisinvention can be used to ensure firm cementing without patient's burden.

This invention also provides a dental adhesion kit consisting of theabove dental adhesive composition of this invention in combination witha dental primer comprising (D) an acidic-group containing polymerizablemonomer; (E) an aryl borate; (F) an organosulfinic acid salt; and (G)water.

An infiltration promoter for a dental adhesive composition called as aprimer is generally applied to a tooth surface to improve adhesivenessof the dental adhesive composition to the tooth before applying thecomposition.

The adhesive composition of this invention can provide a good adhesivestrength when being combined with the primer comprising the above (D) to(G) as well as (H) a polymerizable monomer other than the acidic-groupcontaining polymerizable monomer and (I) an organic solvent. The kit ofthis invention can be used to provide a higher adhesive strength to bothdental enamel and dentin.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Dental Adhesive Composition

(A) Polymerizable Monomer Comprising an Acidic-group ContainingPolymerizable Monomer

In a dental adhesive composition according to this invention, apolymerizable monomer used as component (A) must comprise at least oneacidic-group containing polymerizable monomer. If component (A)comprises no such acidic-group containing polymerizable monomers, thedental adhesive composition does not exhibit good adhesiveness.

An acidic-group containing polymerizable monomer as used herein means acompound containing at least one group that exhibits acidic property inan aqueous solution and at least one polymerizable unsaturated group ina molecule. Examples of the acidic group include a phosphinico group{═P(═O)OH}, a phosphono group {—P(═O)(OH)₂}, a carboxyl group{—C(═O)OH}, a sulfone group (SO₃H) and an organic group containing anacid anhydride structure {—C(═O)—O—C(═O)—}. Examples of a polymerizableunsaturated group include acryloyl group, methacryloyl group, acrylamidegroup, methacrylamide group and styryl group.

Any acidic-group containing polymerizable monomer described above can beused with no limitations, but a compound represented by general formula(1) or (2) is preferable because of its higher adhesive strength to atooth or base metal.

wherein R₁ and R′₁ independently represent hydrogen atom or methylgroup; W and W′ independently represent oxycarbonyl group (—COO—),iminocarbonyl group (—CONH—) or phenylene group (—C₆H₄—); R₂ and R′₂independently represent a single bond or a bivalent to sexavalent C₁ toC₃₀ organic residue optionally containing an ether bond and/or an esterbond, provided that when W is oxycarbonyl group or iminocarbonyl group,R₂ is not a single bond and when W′ is oxycarbonyl group oriminocarbonyl group, R′₂ is not a single bond; X represents a monovalentacidic group; X′ represents a bivalent acidic group; m and m′independently represent an integer of 1 to 4; m+n represents a valencyof R₂; and m′+n′ represents a valency of R′₂.

In general formula (1) or (2), X and X′ may have any structure as longas it is an acidic group as defined above, but is preferably asillustrated below.

In general formula (1) or (2), R₂ may be a single bond or a knownbivalent to sexavalent C₁ to C₃₀ organic residue optionally having anether bond and/or an ester bond, without limitations. Preferableexamples thereof are illustrated below. An expression “R₂ is a singlebond” herein means that W is directly bound to X via a single bond, andwhen W is oxycarbonyl group or iminocarbonyl group, R₂ is not a singlebond. It can be also applied to relationship between R′₂ and W′.

wherein m1, m2 and m3 are independently an integer of 0 to 10 andm1+m2+m3 is one or more.

Preferable examples of an acidic-group containing polymerizable monomerrepresented by general formula (1) or (2) are as follows:

wherein R₁ represents hydrogen atom or methyl group;

wherein R1 represents hydrogen atom or methyl group; 1, m and n in thelast compound independently represent an integer of 0 to 2; and thecompound is often provided as a mixture of compounds having different l,m and n, in which an average of the sum of l+m+n is 3.5;

wherein R₁ represents hydrogen atom or methyl group;

wherein R₁ represents hydrogen atom or methyl group.

Additional examples of the acidic-group containing polymerizable monomerinclude vinylphosphonic acids, acrylic acid, methacrylic acid and vinylsulfonic acid.

The above acidic-group containing polymerizable monomers may be usedalone or in combination of two or more.

Among these acidic-group containing polymerizable monomers illustratedabove, particularly preferable compounds are those containing aphosphinico group {═P(═O)OH}, a phosphono group {—P(═O)(OH)₂}, acarboxyl group {—C(═O)OH} as an acidic group because of their higheradhesive strength to a tooth.

Component (A) in a dental adhesive composition of this invention may becomposed of the acidic-group containing polymerizable monomer alone. Itis, however, preferable that the composition further contain apolymerizable monomer without an acidic group because a cured product ofthe adhesive composition mixture exhibits good strength and adhesiondurability. In particular, a content of the acidic-group containingpolymerizable monomer in the total of polymerizable monomers ascomponent (A) is preferably 3 to 70 wt %, more preferably 5 to 50 wt %because it can improve an adhesive strength to both dental enamel anddentin. If a content of the acidic-group containing polymerizablemonomer is too small, an adhesive strength to a dental enamel tends tobe reduced, while if it is too large, an adhesive strength to a dentintends to be reduced.

A polymerizable monomer without an acidic group may be any known monomerhaving at least one polymerizable unsaturated group in a molecule otherthan the above acidic-group containing polymerizable monomers, withoutlimitations. A polymerizable unsaturated group in the polymerizablemonomer may be selected from those described for the acidic-groupcontaining polymerizable monomer, and preferable examples includeacryloyl group, methacryloyl group, acrylamide group and methacrylamidegroup because of their appropriate curing rate.

Preferable examples of a polymerizable monomer other than acidic-groupcontaining polymerizable monomers include mono(meth)acrylate monomerssuch as methyl (meth)acrylate, ethyl (meth)acrylate, butyl(meth)acrylate, glycidyl (meth)acrylate, 2-cyanomethyl (meth)acrylate,benzyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, allyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl(meth)acrylate and glyceryl mono(meth)acrylate; polyfunctional(meth)acrylate monomers such as ethylene glycol di(meth)acrylate,diethyleneglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate,nonaethyleneglycol di(meth)acrylate, propyleneglycol di(meth)acrylate,dipropyleneglycol di(meth)acrylate,2,2′-bis[4-(meth)acryloyloxyethoxyphenyl]propane,2,2′-bis[4-(meth)acryloyloxyethoxyethoxyphenyl]propane,2,2′-bis[4-(meth)acryloyloxyethoxyethoxyethoxyethoxyethoxyphenyl]propane,2,2′-bis{4-[3-(meth)acryloyloxy-2-hydroxypropoxy]phenyl}propane,1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,1,9-nonandiol di(meth)acrylate, trimethylolpropane tri(meth)acrylate,neopentylglycol di(meth)acrylate,1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane,1,6-bis(methacrylethyloxycarbonylamino)-2,4,4-trimethylhexane, urethane(meth)acrylate and epoxy (meth)acrylate; fumarate monomers such asmonomethyl fumarate, diethyl fumarate and diphenyl fumarate; styrene orα-methyl styrene derivatives such as styrene, divinylbenzene, α-methylstyrene and α-methyl styrene dimer; and allyl compounds such as diallylphthalate, diallyl terephthalate, diallyl carbonate and allyldiglycolcarbonate.

When cementing a noble-metal restorative material for a tooth crown witha tooth, it is preferable to add a polymerizable monomer containing afunctional group capable of binding to the noble metal as apolymerizable monomer without an acidic group in component (A). Examplesof such a polymerizable monomer include functional-group containingmonomers such as derivative of thiouracils, triazine dithiones andmercaptothiazoles. Specific examples include polymerizable monomerswhich can generate a mercapto group by tautomerism, represented bygeneral formulas (3) to (7); polymerizable monomers containing adisulfide groups represented by general formulas (8) to (11); andpolymerizable monomers containing a linear or cyclic thioether grouprepresented by general formulas (12) and (13):

wherein R₃ represents hydrogen atom or methyl group; R₄ represents abivalent C₁ to C₁₂ saturated hydrocarbon group, —CH₂—C₆H₄—CH₂—,—(CH₂)_(o)—Si(CH₃)₂OSi(CH₃)₂—(CH₂)_(p)— where o and p independentlyrepresent an integer of 1 to 5, or —CH₂CH₂OCH₂CH₂—; Z represents —OCO—,—OCH₂— or —OCH₂—C₆H₄— in any of which the carbon atom at the right endis bound to an unsaturated carbon atom while the oxygen atom at the leftend is bound to R₄; Z′ is —OCO—, —C₆H₄— or a single bond, provided thatwhen it is —OCO—, the carbon atom at the right end is bound to anunsaturated carbon atom while the oxygen atom at the left end is boundto R₄; Y is —S—, —O— or —N(R′)— where R′ is hydrogen atom or C₁ to C₅alkyl group. An expression “Z′ is a single bond” herein means that R₄and an unsaturated carbon is bound directly.

Among specific examples of such a compound, examples of a polymerizablemonomer which can generate a mercapto group by tautomerism, representedby general formulas (3) to (7) are as follows.

Examples of a polymerizable monomer having a disulfide group representedby general formulas (8) to (11) are as follows.

Examples of a polymerizable monomer having a linear or cyclic thioethergroup represented by general formulas (12) and (13) are as follows.

These polymerizable monomers having a functional group capable of beingbound to a noble metal may be used alone or in combination of two ormore. A content of these polymerizable monomers can be appropriatelydetermined, taking a viscosity of a composition and mechanical strengthof a cured product of an adhesive composition into consideration, and isgenerally 0.1 to 50 wt parts, more preferably 0.2 to 20 wt parts to 100wt parts of the total amount of polymerizable monomers.

There are no restrictions to a content of a polymerizable monomercomprising an acidic-group containing polymerizable monomer as component(A) in an adhesive composition of this invention. It is, however,preferably 25 to 65 wt parts, more preferably 30 to 60 wt parts,particularly preferably 35 to 55 wt parts to 100 wt parts of the totalamount of a polymerizable monomer comprising an acidic-group containingpolymerizable monomer as component (A), a non-crosslinking polymerfiller as component (B) and a polymerization initiator as component (C),in order to maintain solubility of the non-crosslinking polymer fillerand a working time within preferable ranges.

(B) A Spherical Filler Substantially Consisting of Non-crosslinkingPolymethyl Methacrylate and a Spherical Filler Substantially Consistingof Non-crosslinking Polyethyl Methacrylate

Component (B) in an adhesive composition of this invention comprises asessential ingredients a spherical filler substantially consisting ofnon-crosslinking polymethyl methacrylate (hereinafter, referred to as a“PMMA spherical filler”) and a spherical filler substantially consistingof non-crosslinking polyethyl methacrylate (hereinafter, referred to asa “PEMA spherical filler”). If component (B) is not a mixture of thesetwo fillers, an appropriate working time cannot be achieved.

For example, if component (B) consists of the PMMA spherical filleralone, a dissolution rate to a polymerizable monomer of component (A) issignificantly reduced and the filler is not so compatible with themonomer, so that it takes a longer time to dissolve the filler until ithas properties suitable to handling. If only the PEMA spherical filleris employed, a working time is extremely reduced.

There are no restrictions to the PMMA and the PEMA spherical fillersused as component (B) as long as they are substantiallynon-crosslinking. Examples of these fillers are spherical polymersprepared by suspension polymerization or emulsion polymerization ofmethyl methacrylate or ethyl methacrylate without using a crosslinkingagent. Such spherical fillers are commercially and industriallyavailable. The term “substantially non-crosslinking” as used hereinmeans that most of a polymer is dissolved in a monomer component ascomponent (A). If a crosslinking density is too high for the fillerpolymer to be dissolved in the monomer, mixing of these componentscannot give good handling properties due to poor compatibility and alsocannot give a good adhesive strength. The term “spherical” as usedherein means that a filler has a generally round shape without anacute-angle part as is found in a pulverized filler, and thus does notnecessarily means an entirely spheric shape.

The PMMA and PEMA spheric fillers must not be necessarily homopolymersof methyl methacrylate and ethyl methacrylate, respectively. They may becopolymers with a different monomer as long as the other monomer iscontained within a range that it does not adversely affect the effectsdesired in this invention (generally, 10 mol % or less based on themonomer amount). Examples of the different monomer include alkyl(meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate,propyl (meth)acrylate, butyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate and 3-hydroxypropyl(meth)acrylate; and styrene monomers such as styrene, α-methylstyreneand para-methylstyrene.

There are no restrictions to a weight average molecular weight of eachpolymer in a PMMA or PEMA spherical filler used. However, the PMMAspherical filler is suitably a mixture of a spherical filler consistingof a non-crosslinking polymethyl methacrylate having a weight averagemolecular weight of less than 100,000 (hereinafter, referred to as alow-molecular weight PMMA spherical filler) and a spherical fillerconsisting of a non-crosslinking polymethyl methacrylate having a weightaverage molecular weight of 100,000 or more (hereinafter, referred to asa high-molecular weight PMMA spherical filler), improving compatibilityof the fillers and monomers when the dental adhesive composition mixtureof the present invention is cured. A mixing ratio between the sphericalfiller consisting of a non-crosslinking polymethyl methacrylate having aweight average molecular weight of less than 100,000 and the sphericalfiller consisting of a non-crosslinking polymethyl methacrylate having aweight average molecular weight of 100,000 or more is preferably 10:90to 70:30 by weight.

There are no restrictions to a weight average molecular weight of thenon-crosslinking polyethyl methacrylate constituting the PEMA sphericalfiller because it does not significantly influence a working time, andcommonly available fillers generally have a weight average molecularweight of about 100,000 to 500,000. Herein, a weight average molecularweight is a molecular weight converted into polystyrene as determined bygel permeation chromatography.

There are no restrictions to a particle size of a PMMA or PEMA sphericalfiller. It, however, preferably has an average particle size of 0.1 to50 μm, particularly preferably 1 to 40 μm in the light of reduction in afilm thickness and a higher adhesive strength of an adhesivecomposition.

A mixing ratio between a PMMA and a PEMA spherical fillers influences aworking time. An optimal ratio cannot be particularly defined because itis dependent on a particle size of a filler used and a molecular weightof a polymer constituting the filler. A proportion of the amount of thePMMA spherical filler to the total amount of non-crosslinking polymerfillers is generally 85 to 98 wt %. Within this range, a suitable rangemay be appropriately determined, taking a working time and a curing timein each system into consideration. A mixing ratio can be determined suchthat a working time of an adhesive composition determined at roomtemperature (23° C.) is 40 to 150 sec, preferably 60 to 120 sec and acuring time determined at 37° C. is 3 to 5 min. Generally, a largerratio of the PMMA spherical filler tends to increase a working time andthus a curing time.

A working time as used above is defined a time period from a start timewhen after adding component (B) to component (A) at a room temperature(23° C.) the mixture has an appropriate viscosity, i. e., the mixturebecomes viscous such that it can be taken with the spatula, by stirringthe mixture with a stirring spatula for a few (2 to 3) seconds with aninterval of 5 sec to an endpoint when a viscosity of the mixture isincreased such that the mixture can be taken as a thread with thespatula (i. e., a period during which a viscosity is proper forhandling).

If it takes a longer time to increase a viscosity of the mixture to theabove proper level (a proper-viscosity reaching time) by stirring, theadhesive composition remains to be a low-viscosity liquid for a longtime. Since the composition cannot be applied to a tooth during theperiod, a dentist must continue stirring until a proper viscosity isprovided, which is a clinically troublesome procedure. A mixing ratio ofthese two fillers is, therefore, preferably determined such that aproper-viscosity reaching time becomes 10 to 40 sec, particularly 20 to35 sec.

A curing time is determined as follows. After blending components (A),(B) and (C), the mixture is stirred as described above. A sample mixturewhose viscosity has reached a proper level is observed for its restcuring behavior at 37° C. using a differential scanning calorimeter(DSC) to determine a time until the maximum curing heat is observed. Acuring time is a period from mixing to the time of the maximum curingheat in the above procedure.

There are no restrictions to a content of component (B) in an adhesivecomposition of this invention. It is, however, preferably 35 to 70 wtparts, more preferably 40 to 65 wt parts, particularly 45 to 60 wt partsto 100 wt parts of the total of components (A), (B) and (C).

(c) Polymerization Initiator

There are no restrictions to a polymerization initiator as component (C)used in an adhesive composition of this invention, and anychemical-polymerization initiator or photopolymerization initiator usedin a conventional dental curable composition can be used withoutlimitations. Tributylboran or its partially oxidized as a polymerizationinitiator has disadvantages that it must be enclosed in a specialsyringe while being separated from other components and it reduces acuring rate, but they can be used.

Chemical-polymerization initiators which can be used in this inventioninclude redox type initiators such as an organic peroxide/an amine andan organic peroxide/an amine/a sulfinic acid salt; an organometallicinitiator which initiate polymerization by reacting with an acid; and a(thio)balbituric acid derivative/cupric ion/a halogenated compound.

Preferable examples of the above organic peroxide include t-butylhydroperoxide, cumene hydroperoxide, di-t-butyl peroxide, dicumylperoxide, acetyl peroxide, lauroyl peroxide and benzoyl peroxide.Examples of the amine preferably include secondary and tertiary amines,in which an amino group is attached to an aryl group such asN,N-dimethyl-p-toluidine, N,N-dimethylaniline,N-(2-hydroxyethyl)aniline, N,N-di(2-hydroxyethyl)-p-toluidine,N-methylaniline and N-methyl-p-toluidine. Examples of the above sulfinicacid salt which can be suitably used include sodium benzenesulfinate,lithium benzenesulfinate, sodium p-toluenesulfinate, lithiump-toluenesulfinate, potassium p-toluenesulfinate, sodiumm-nitrobenzenesulfinate and sodium p-fluorobenzenesulfinate.

An organometallic polymerization initiator which can initiatepolymerization by reacting with an acid is suitably an aryl boraterepresented by general formula (14) described later. Preferable examplesof the above (thio)balbituric acid derivative include 5-butyl(thio)balbituric acid, 1,3,5-trimethyl (thio)balbituric acid,1-benzyl-5-phenyl (thio)balbituric acid, 1-cyclohexyl-5-methyl(thio)balbituric acid and 1-cyclohexyl-5-butyl (thio)balbituric acid.Preferable examples of the above halogenated compound includedilauryl-dimethyl-ammonium chloride, lauryl-dimethylbenzyl-ammoniumchloride, benzyl-trimethylammonium chloride, tetramethyl-ammoniumchloride, benzyl-dimethyl-cetyl-ammonium chloride anddilauryl-dimethyl-ammonium bromide.

A photopolymerization initiator which can be used in this invention mayconsist of a photosensitizer alone; a photosensitizer/aphotopolymerization promoter; a dye/a photoacid generator/a sulfinicacid salt; or a dye/a photoacid generator/an aryl borate.

Examples of a photosensitizer include α-diketones such ascamphorquinone, benzil, α-naphthyl, acenaphthene, naphthoquinone,p,p′-dimethoxybenzil, p,p′-dichlorobenzylacetyl,1,2-phenanthrenequinone, 1,4-phenanthrenequinone,3,4-phenanthrenequinone and 9,10-phenanthrenequinone; thioxanthones suchas 2,4-diethylthioxanthone; α-aminoacetophenones such as2-benzyl-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-benzyl-diethylamino-1-(4-morpholinophenyl)-butanone-1,2-benzyl-dimethylamino-1-(4-morpholinophenyl)-propanone-1,2-benzyl-diethylamino-1-(4-morpholinophenyl)-propanone-1,2-benzyl-dimethylamino-1-(4-morpholinophenyl)-pentanone-1and 2-benzyl-diethylamino-1-(4-morpholinophenyl)-pentanone-1; andacylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphineoxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide andbis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

Preferable examples of a photopolymerization promoter include tertiaryamines such as N,N-dimethylaniline, N,N-diethylaniline,N,N-di-n-butylaniline, N,N-dibenzylaniline, N,N-dimethyl-p-toluidine,N,N-diethyl-p-toluidine, N,N-dimethyl-m-toluidine,p-bromo-N,N-dimethylaniline, m-chloro-N,N-dimethylaniline,p-dimethylaminobenzaldehyde, p-dimethylaminoacetophenone,p-dimethylaminobenzoic acid, ethyl p-dimethylaminobenzoate, amylp-dimethylaminobenzoate, methyl N,N-dimethylanthranate,N,N-dihydroxyethylaniline, N,N-dihydroxyethyl-p-toluidine,p-dimethylaminophenetyl alcohol, p-dimethylaminostilbene,N,N-dimethyl-3,5-xylidine, 4-dimethylaminopyridine,N,N-dimethyl-α-naphthylamine, N,N-dimethyl-β-naphthylamine,tributylamine, tripropylamine, triethylamine, N-methyldiethanolamine,N-ethyldiethanolamine, N,N-dimethylhexylamine, N,N-dimethyldodecylamine,N,N-dimethylstearylamine, N,N-dimethylaminoethyl methacrylate,N,N-diethylaminoethyl methacrylate and 2,2′-(n-butylimino)diethanol; andbalbituric acids such as 5-butylbalbituric acid and1-benzyl-5-phenylbalbituric acid.

Preferable examples of a dye include 3-thienoylcoumarin,3-(4-methoxybenzoyl)coumarin, 3-benzoylcoumarin,3-(4-cyanobenzoyl)coumarin, 3-thienoyl-7-methoxycoumarin,7-methoxy-3-(4-methoxybenzoyl)coumarin, 3-benzoyl-7-methoxycoumarin,3-(4-cyanobenzoyl)-7-methoxycoumarin,5,7-dimethoxy-3-(4-methoxybenzoyl)coumarin,3-benzoyl-5,7-dimethoxycoumarin,3-(4-cyanobenzoyl)-5,7-dimethoxycoumarin,3-acetyl-7-dimethylaminocoumarin, 7-diethylamino-3-thienoylcoumarin,7-diethylamino-3-(4-methoxybenzoyl)coumarin,3-benzoyl-7-diethylaminocoumarin,7-diethylamino-3-(4-cyanobenzoyl)coumarin,7-diethylamino-3-(4-dimethylaminobenzoyl)coumarin,3-cinnamoyl-7-diethylaminocoumarin,3-(p-diethylaminocinnamoyl)-7-diethylaminocoumarin,3-acetyl-7-diethylaminocoumarin, 3-carboxy-7-diethylaminocoumarin,3-(4-carboxybenzoyl)-7-diethylaminocoumarin, 3,3′-carbonylbiscoumarin,3,3′-carbonylbis(7-diethylamino)coumarin,2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-10-(benzothiazolyl)-11-oxo-1H,5H,11H-[1]benzopyrano[6,7,8,ij]quinolizine,3,3′-carbonylbis(5,7-)dimethoxy-3,3′-biscoumarin,3-(2′-benzimidazolyl)-7-diethylaminocoumarin,3-(2′-benzoxazolyl)-7-diethylaminocoumarin,3-(5′-phenylthiadiazolyl)-7-diethylaminocoumarin,3-(2′-benzthiazolyl)-7-diethylaminocoumarin and3,3′-carbonylbis(4-cyano-7-diethylamino)coumarin.

Examples of a photoacid generator which can be used includehalomethyl-substituted-s-triazines such as2,4,6-tris(trichloromethyl)-s-triazine,2,4,6-tris(tribromomethyl)-s-triazine,2-methyl-4,6-bis(trichloromethyl)-s-triazine,2-methyl-4,6-bis(tribromomethyl)-s-triazine,2-phenyl-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-methylthiophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-chlorophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(2,4-dichlorophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-bromophenyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine,2-n-propyl-4,6-bis(trichloromethyl)-s-triazine,2-(α,α,β-trichloroethyl)-4,6-bis(trichloromethyl)-s-triazine,2-styryl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,2-(o-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,2-(p-butoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,2-(3,4-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine and2-(3,4,5-trimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine; anddiphenyliodonium salts such as diphenyliodonium,bis(p-chlorophenyl)iodonium, ditolyliodonium,bis(p-tert-butylphenyl)iodonium, bis(m-nitrophenyl)iodonium,p-tert-butylphenylphenyliodonium, methoxyphenylphenyliodonium andp-octyloxyphenylphenyliodonium chlorides, bromides, tetrafluoroborates,hexafluorophosphates, hexafluoroarsenates, hexafluoroantimonates andtrifluoromethanesulfonates.

As a sulfinic acid salt, those specifically listed for the redox typepolymerization initiator can be also used and as an arylborate compound,those represented by general formula (14) described later can be used.

These polymerization initiators can be, as appropriate, added alone orin combination of two or more.

In a dental adhesive composition of this invention, a chemicalpolymerization initiator consisting of a combination of a peroxide suchas benzoyl peroxide and an amine such as dimethyl-p-toluidine can besuitably used as component (C), a polymerization initiator, because itcan provide an improved adhesive strength and allows a polymerizationrate (curing rate) to be properly adjusted. When a dental adhesivecomposition of this invention is of a dual curing type, it is suitablein the light of an adhesive strength and improvement in polymerizabilityto use the above chemical polymerization initiator in combination with aphotopolymerization initiator consisting of a combination of anα-diketone such as camphorquinone and an amine such as ethyldimethylaminobenzoate or of an acylphosphine oxide derivative such asbis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

The content of a polymerization initiator as component (C) in a dentaladhesive composition of this invention is not particularly limited aslong as it is sufficient to initiate polymerization of monomercomponents, and it is preferably 0.01 to 20 wt parts to 100 wt parts ofthe total amount of polymerizable monomers as component (A) in the lightof improvement in physical properties such as weather resistance of acured product.

In addition to component (B), a dental adhesive composition of thisinvention can contain an inorganic filler for adjusting physicalproperties such as cured-product strength for the composition. Theinorganic filler may be selected from common inorganic fillers withoutlimitations.

Examples of an inorganic filler which can be used in this inventioninclude quartz, silica, silica-alumina, silica-titania, silica-zirconia,silica-magnesia, silica-calcia, silica-barium oxide, silica-strontiumoxide, silica-titania-sodium oxide, silica-titania-potassium oxide,silica-zirconia-sodium oxide, silica-zirconia-potassium oxide, titania,zirconia and alumina.

An ion-releasing filler which can release cations in an acidic solutionmay be also suitably used. Examples of such an ion-releasing fillerinclude hydroxides such as calcium hydroxide and strontium hydroxide;zinc oxide; silicate glass; fluoroaluminosilicate glass; barium glass;and strontium glass. Among these, fluoroaluminosilicate glass is mostpreferable in that its cured product exhibits good stain resistance. Thefluoroaluminosilicate glass may be selected from those known for adental cement. A commonly used fluoroaluminosilicate glass has thefollowing composition: 10 to 33% of silicon; 4 to 30% of aluminum; 5 to36 of alkaline earth metals; 0 to 10% of alkali metals; 0.2 to 16% ofphosphorous; 2 to 40% of fluorine; and the remaining amount of oxygen inan ion-weight percent. Suitable are those having the above composition,those in which a part or all of the alkaline earth metal component isreplaced with magnesium, strontium and/or barium, and those containingstrontium for providing a cured product with X-ray opacity and improvedstrength.

These inorganic fillers may be preferably coated with a methacrylatepolymer such as polymethyl methacrylate and polyethyl methacrylate forimproving compatibility with the above polymerizable monomers. Aninorganic-organic composite filler such as ground complex of inorganicoxide and polymer may be also used.

There are no restrictions to a shape of such a filler, and thus it maybe presented as pulverized particles prepared by common grinding orspherical particles. There are no restrictions to a particle size of thefiller and it is preferably 50 μm or less, more preferably 30 μm or lessfor providing a film thickness required for good adhesion of aprosthesis to a tooth.

In a dental adhesive composition of this invention, an organic solvent,a thickener or the like may be added for adjusting a viscosity of thecomposition as long as the additive does not deteriorate performance ofthe composition. An organic solvent is desirably selected from thosewhich are not harmful to a living body, preferably including ethanol,propanol, ethyleneglycol, propane diol and acetone. Such an organicsolvent may be, if necessary, a mixture of two or more organic solvents.Furthermore, a small amount of a polymerization inhibitor may bepreferably added for improving storage stability and environmental lightstability, including hydroquinone, hydroquinone monomethyl ether and2,6-di-tert-butylphenol. If necessary, an appropriate amount of acolorant may be added to a dental adhesive composition of thisinvention. Their contents may be determined as usual.

In a dental adhesive composition of this invention, mixing of component(B) and component (A) results in increase in a viscosity of the mixturebecause of dissolution of component (B). It is, therefore, preferable toseparately prepare these components for preventing them from being mixedeach other and then to mix them immediately before use. Generally,component (A) and component (B) are separately packed. A polymerizationinitiator as component (C) can be packed as a premix with component (A)or (B) in a condition of preventing initiation of polymerization.

Primer

When using a dental adhesive of this invention for, e. g., restoring atooth, the tooth usually undergoes primer treatment that an infiltrationpromoter known as a primer is applied on the surface of the tooth beforeapplying the composition. This primer treatment is conducted forimproving adhesiveness. The primer may be any of known dental primers.

A dental adhesive composition of this invention may be used incombination with a dental primer comprising (D) an acidic-groupcontaining polymerizable monomer, (E) an aryl borate, (F) anorganosulfinic acid salt and (G) water, to provide further improvedadhesion performance.

A dental adhesive composition of this invention may be used incombination with a dental primer comprising (D) an acidic-groupcontaining polymerizable monomer, (E) an aryl borate, (F) anorganosulfinic acid salt, (G) water, (H) a polymerizable monomer otherthan the acidic-group containing polymerizable monomer and (I) anorganic solvent, to provide further improved adhesion performance.

A dental adhesive composition of this invention may be used incombination with the primer composition as a kit (the present kit), toachieve both good operability and improved adhesive strength.

(D) Acidic-group Containing Polymerizable Monomer

Component (D) in a primer composition used in the present kit is anacidic-group containing polymerizable monomer. The acidic-groupcontaining polymerizable monomer is as described for the acidic-groupcontaining polymerizable monomer in component (A) described above. Theacidic-group containing polymerizable monomer used as component (D) mustnot be necessarily the same as that in combination therewith ascomponent (A) in the dental adhesive composition of this invention.Monomers used as component (D) may be used alone or in combination oftwo or more, as appropriate. A content of component (D) is 1 to 50 wtparts, preferably 2 to 30 wt parts, more preferably 3 to 25 wt parts to100 wt parts of the total of the primer components in the light ofimprovement in adhesiveness to a dental enamel and a dentin.

(E) Aryl Borate

An aryl borate used as component (E) in the above primer composition isa borate having at least one boron-aryl bond in one molecule. A boratewithout an intramolecular boron-aryl bond exhibit inadequate storagestability. An aryl borate suitably used in this invention may berepresented by general formula (14):

wherein R₅, R₆ and R₇ are independently optionally substituted alkylgroup, aryl group, aralkyl group or alkenyl group; R8 and R9 areindependently hydrogen atom, halogen atom, nitro group, optionallysubstituted alkyl group, optionally substituted alkoxyl group oroptionally substituted phenyl group; L⁺ is a metal cation, a quaternaryammonium ion, a quaternary pyridinium ion, a quaternary quinolinium ionor a phosphonium ion.

Among the above aryl borates, aryl borates which can be suitably usedwill be specifically described.

Examples of a borate having one aryl group include sodium salts, lithiumsalts, potassium salts, magnesium salts, tetrabutylammonium salts,tetramethylammonium salts, tetraethylammonium salts, triethanolaminesalts, methylpyridinium salts, ethylpyridinium salts, butylpyridiniumsalts, methylquinolium salts, ethylquinolium salts and butylquinoliniumsalts of trialkylphenylborons, trialkyl(p-chlorophenyl)borons,trialkyl(p-fluorophenyl)borons,trialkyl(3,5-bistrifluoromethyl)phenylborons,trialkyl[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]borons,trialkyl(p-nitrophenyl)borons, trialkyl(m-nitrophenyl)borons,trialkyl(p-butylphenyl)borons, trialkyl(m-butylphenyl)borons,trialkyl(p-butyloxyphenyl)borons, trialkyl(m-butyloxyphenyl)borons,trialkyl(p-octyloxyphenyl)borons and trialkyl(m-octyloxyphenyl)borons,where the alkyl group includes n-butyl group, n-octyl group andn-dodecyl group and the like.

Examples of a borate having two aryl groups include sodium salts,lithium salts, potassium salts, magnesium salts, tetrabutylammoniumsalts, tetramethylammonium salts, tetraethylammonium salts,tributylamine salts, triethanolamine salts, methylpyridinium salts,ethylpyridinium salts, butylpyridinium salts, methylquinolium salts,ethylquinolium salts and butylquinolinium salts ofdialkyl-diphenylborons, dialkyl-di(p-chlorophenyl)borons,dialkyl-di(p-fluorophenyl)borons,dialkyl-di(3,5-bistrifluoromethyl)phenylborons,dialkyl-di[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]borons,dialkyl-di(p-nitrophenyl)borons, dialkyl-di(m-nitrophenyl)borons,dialkyl-di(p-butylphenyl)borons, dialkyl-di(m-butylphenyl)borons,dialkyl-di(p-butyloxyphenyl)borons, dialkyl-di(m-butyloxyphenyl)borons,dialkyl-di(p-octyloxyphenyl)borons anddialkyl-di(m-octyloxyphenyl)borons, where the alkyl group is asdescribed above.

Examples of a borate having three aryl groups include sodium salts,lithium salts, potassium salts, magnesium salts, tetrabutylammoniumsalts, tetramethylammonium salts, tetraethylammonium salts,tributylamine salts, triethanolamine salts, methylpyridinium salts,ethylpyridinium salts, butylpyridinium salts, methylquinolium salts,ethylquinolium salts and butylquinolinium salts ofmonoalkyl-triphenylborons, monoalkyl-tri(p-chlorophenyl)borons,monoalkyl-tri(p-fluorophenyl)borons,monoalkyl-tri(3,5-bistrifluoromethyl)phenylborons,monoalkyl-tri[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]borons,monoalkyl-tri(p-nitrophenyl)borons, monoalkyl-tri(m-nitrophenyl)borons,monoalkyl-tri(p-butylphenyl)borons, monoalkyl-tri(m-butylphenyl)borons,monoalkyl-tri(p-butyloxyphenyl)borons,monoalkyl-tri(m-butyloxyphenyl)borons, monoalkyl-tri(p-octyloxyphenyl)borons andmonoalkyl-tri(m-octyloxyphenyl)borons, where the alkyl group includen-butyl group, n-octyl group and n-dodecyl group and the like.

Examples of a borate having four aryl groups include sodium salts,lithium salts, potassium salts, magnesium salts, tetrabutylammoniumsalts, tetramethylammonium salts, tetraethylammonium salts,tributylamine salts, triethanolamine salts, methylpyridinium salts,ethylpyridinium salts, butylpyridinium salts, methylquinolium salts,ethylquinolium salts and butylquinolinium salts of tetraphenylboron,tetrakis(p-chlorophenyl)boron, tetrakis(p-fluorophenyl)boron,tetrakis(3,5-bistrifluoromethyl)phenylboron,tetrakis[3,5-bis(1,1,1,3,3,3-hexafluoro-2-methoxy-2-propyl)phenyl]boron,tetrakis(p-nitrophenyl)boron, tetrakis(m-nitrophenyl)boron,tetrakis(p-butylphenyl)boron, tetrakis(m-butylphenyl)boron,tetrakis(p-butyloxyphenyl)boron, tetrakis(m-butyloxyphenyl)boron,tetrakis(p-octyloxyphenyl)boron and tetrakis(m-octyloxyphenyl)boron.

Among these, a borate having three or four aryl groups may be suitablyused for further improving storage stability. Furthermore, a boratehaving four aryl groups is most preferable because of its good handlingproperties and availability. The aryl borates may be used alone or incombination of two or more.

The aryl borate is preferably used at 0.01 to 25 wt parts to 100 wtparts of the total of the polymerizable monomers in the primercomposition, i. e., the total of an acidic-group containingpolymerizable monomer as component (D) and other polymerizable monomersadded as optional components. Its content is more preferably 0.05 to 15wt parts in the light of good polymerization properties in an adhesiveinterface and a higher adhesive strength.

(F) Organosulfinic Acid Salt

An organosulfinic acid salt as component (F) in a dental primer in thepresent kit may be selected from alkali metal, alkaline earth metal andammonium salts of known organosulfinic acids. Examples of the alkalimetal salt include lithium, sodium and potassium salts. Examples of thealkaline earth metal salt include magnesium, calcium, strontium andbarium salts. Examples of the amine salt include primary ammonium saltssuch as methylamine, ethylamine, propylamine, butylamine, aniline,toluidine, phenylenediamine and xylylenediamine salts; secondaryammonium salts such as dimethylamine, diethylamine, dipropylamine,dibutylamine, piperidine, N-methylaniline, N-ethylaniline, diphenylamineand N-methyltoluidine; tertiary ammonium salts such as trimethylamine,triethylamine, pyridine, N,N-di(β-hydroxyethyl)aniline,N,N-diethylaniline, N,N-dimethyltoluidine andN,N-di(β-hydroxyethyl)toluidine salts; and quaternary ammonium saltssuch as tetramethylammonium, tetraethylammonium, tetrapropylammonium,and trimethylbenzylammonium salts.

A suitable organosulfinic acid which may form a salt with these metalsand amines may be a known sulfinic acid such as alkylsulfinic acids,alicyclic sulfinic acids and aromatic sulfinic acids.

Examples of an organosulfinic acid salt include alkylsulfinic acid saltssuch as sodium ethanesulfinate, lithium ethanesulfinate, sodiumpropanesulfinate, calcium hexanesulfinate, sodium octanesulfinate,sodium decanesulfinate and sodium dodecanesulfinate; alicyclic sulfinicacid salts such as sodium cyclohexanesulfinate and sodiumcyclooctanesulfinate; and aromatic sulfinic acid salts such as lithiumbenzenesulfinate, sodium benzenesulfinate, potassium benzenesulfinate,magnesium benzenesulfinate, calcium benzenesulfinate, strontiumbenzenesulfinate, barium benzenesulfinate, butylamine benzenesulfinate,aniline benzenesulfinate, toluidine benzenesulfinate, phenylenediaminebenzenesulfinate, diethylamine benzenesulfinate, diphenylaminebenzenesulfinate, triethylamine benzenesulfinate, ammoniumbenzenesulfinate, tetramethylammonium benzenesulfinate,trimethylbenzylammonium benzenesulfinate, lithium o-toluenesulfinate,sodium o-toluenesulfinate, calcium o-toluenesulfinate, cyclohexylamineo-toluenesulfinate, aniline o-toluenesulfinate, ammoniumo-toluenesulfinate, tetraethylammonium o-toluenesulfinate, lithiump-toluenesulfinate, sodium p-toluenesulfinate, potassiump-toluenesulfinate, barium p-toluenesulfinate, ethylaminep-toluenesulfinate, toluidine p-toluenesulfinate, N-methylanilinep-toluenesulfinate, pyridinium p-toluenesulfinate, ammoniump-toluenesulfinate, tetrabutylammonium p-toluenesulfinate, sodiumβ-naphthalenesulfinate, strontium β-naphthalenesulfinate, triethylamineβ-naphthalenesulfinate, N-methyltoluidine β-naphthalenesulfinate,ammonium β-naphthalenesulfinate and trimethylbenzylammoniumβ-naphthalenesulfinate.

Among these sulfinic acid salts, sodium and lithium salts of aromaticsulfinates are preferable because of their catalytic activity to a toothand availability. These organic sulfinic acid salts may be used alone orin combination of two or more.

An organic sulfinic acid salt is preferably added at 0.01 to 25 wt partsto 100 parts of the total amount of polymerizable monomers in the primercomposition, more preferably at 0.05 to 15 wt parts in the light ofhigher polymerizability in an adhesion interface and an improvedadhesive strength.

(G) Water

Preferably, component (G), water, in the primer composition in thepresent kit is substantially free from impurities which are detrimentalto storage stability, biocompatibility or adhesiveness. The types ofwater which can be used include deionized water and distilled water.Water is contained at 5 to 95 wt parts, preferably 20 to 80 wt parts,more preferably 30 to 75 wt parts to 100 parts of the total ofcomponents in the primer for improving an adhesive strength to bothdental dentin and enamel.

(H) Polymerizable Monomer other than the Acidic-group ContainingPolymerizable Monomer

A dental primer composition used in the present kit preferably comprisesa polymerizable monomer other than the acidic-group containingpolymerizable monomer as component (H) for adjusting a viscosity,improving strength or adjusting other physical properties in the primercomposition. A polymerizable monomer as component (H) may be selectedfrom those listed for a polymerizable monomer other than an acidic-groupcontaining polymerizable monomer in component (A) in a dental adhesivecomposition of this invention. This polymerizable monomer must not benecessarily the same as that used as component (A) in the dentaladhesive composition of this invention. Such monomers may be used aloneor in combination of two or more, as appropriate.

A content of component (H) is preferably 5 to 100 wt parts, morepreferably 10 to 75 wt parts to 100 wt parts of component (D).

(I) Organic Solvent

A dental primer used in the present kit preferably comprises an organicsolvent as component (I). The organic solvent is added for dissolving,if used, non-aqueous polymerizable monomers to give a homogeneoussolution.

Examples of an organic solvent include water-miscible organic solventsincluding alcohols and ethers such as methanol, ethanol, 1-propanol,2-propanol, isopropanol, 1-butanol, 2-butanol, 2-methyl-1-propanol,2-methyl-2-propanol, 2-methyl-2-butanol, 2-propen-1-ol, 2-propyn-1-ol,1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol,1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, hexyleneglycol,glycerol, 1,2,6-hexanetriol, trimethylolpropane, diethyleneglycol,triethyleneglycol, tetraethyleneglycol, propyleneglycol,dipropyleneglycol, tripropyleneglycol, 2-methoxyethanol,2-ethoxyethanol, 2-(methoxyethoxy)ethanol, 2-(ethoxyethoxy)ethanol,triethyleneglycol monomethyl ether, triethyleneglycol monoethyl ether,2-isopropoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol,1-ethoxy-2-propanol, dipropyleneglycol monomethyl ether,tripropyleneglycol monomethyl ether, 1,3-dioxolane, tetrahydrofuran,dioxane, propylene oxide, dimethoxymethane, 1,2-dimethoxyethane,1,2-diethoxyethane, bis(2-methoxyethyl) ether and bis(2-ethoxyethyl)ether; ketones such as acetone and methyl ethyl ketone; phosphates suchas hexamethyl phosphate triamide; amides such as dimethylformamide anddimethylacetoamide; carboxylic acids such as acetic acid and propionicacid; sulfur oxides such as dimethyl sulfoxide and sulfolane.

Among these water-miscible organic solvents, ethanol, isopropanol andacetone are most preferable because of lack of harmful effects to aliving body.

A dental primer used in the present kit may comprise, if necessary, avariety of additives such as a polymerization inhibitor, inorganic ororganic particles and a dye as a colorant as long as advantages of thisinvention are not impaired.

A polymerization inhibitor may be added to prevent the primer fromgelating during storage, resulting in improvement in its storagestability. Examples of such a polymerization inhibitor includehydroquinone, hydroquinone monomethyl ether and 2,6-di-tert-butylphenol.

Inorganic or organic particles may be added to the primer to adjust aviscosity and fluidity of the primer. Examples of such particles includedry silica, wet silica and polymethyl methacrylate. These particlespreferably have a primary particle size of 0.001 μm to 1 μm.

A style of packaging a primer used in the present kit may beappropriately determined, taking storage stability into account. Forexample, when an easily hydrolyzable component is present, thehydrolyzable component is separated from water or a compound which mayact as a catalyst for hydrolysis such as an acid, and they can becombined immediately before use.

In using the present kit, the dental primer is applied on a toothsurface using a sponge or small brush, drying the applied surface, afterseveral seconds to several minutes, by air blowing, then coating thepre-treated tooth surface with a dental adhesive composition of thisinvention and then applying a variety of restorative materials on thesurface.

EXAMPLES

This invention will be concretely described with reference to, but notlimited to, examples.

Abbrebiations used in Examples and Comparative Examples have thefollowing meanings.

(1) Acidic-group containing polymerizable monomers, used as component(A) or (D)

PM: a 1:2 (wt/wt) mixture of 2-methacryloyloxyethyl dihydrogenphosphateand bis(2-methacryloyloxyethyl) hydrogenphosphate;

MAC-10: 11-methacryloyloxy-1,1-undecane dicarboxylic acid;

4-META: 4-methacryloyloxyethyl-trimellitic anhydride.

(2) Polymerizable monomers other than an acidic-group containingpolymerizable monomer, used as component (A) or (H) Bis-GMA:

2,2,-bis(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl)propane;

3G: triethyleneglycol dimethacrylate;

D-2.6E: 2,2-bis[(4-methacryloyloxypolyethoxyphenyl)propane];

HEMA: 2-hydroxyethyl methacrylate;

MMA: methyl methacrylate;

TMPT: trimethylol propanetrimethacrylate;

UDMA: a 1:1 (wt/wt) mixture of1,6-bis(methacrylethyloxycarbonylamino)-2,2,4-trimethylhexane and1,6-bis(methacrylethyloxycarbonylamino)-2,4,4-trimethylhexane.

(3) Non-crosslinking polymer fillers, used component (B)

PMMA1: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 30 μm and a weight average molecular weight of250,000;

PMMA2: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 10 μm and a weight average molecular weight of500,000;

PMMA3: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 10 μm and a weight average molecular weight of250,000;

PMMA4: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 20 μm and a weight average molecular weight of1,000,000;

PMMA5: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 10 μm and a weight average molecular weight of50,000;

PMMA6: non-crosslinking spherical polymethyl methacrylate with anaverage particle size of 10 μm and a weight average molecular weight of15,000;

PEMA1: non-crosslinking spherical polyethyl methacrylate with an averageparticle size of 10 μm and a weight average molecular weight of 500,000;

PEMA2: non-crosslinking spherical polyethyl methacrylate with an averageparticle size of 10 μm and a weight average molecular weight of 250,000;

PEMA3: non-crosslinking spherical polyethyl methacrylate with an averageparticle size of 30 μm and a weight average molecular weight of 250,000.

(4) Polymerization initiators, used as component (C)

BPO: benzoyl peroxide;

DMPT: N,N-dimethyl-p-toluidine;

CQ: camphorquinone;

DMBE: ethyl N,N-dimethyl-p-aminobenzoate.

(5) Aryl borates, used as component (E)

PhBNa: sodium tetraphenylborate;

PhBTEOA: tetraphenylboron triethanolamine salt;

FPhBNa: sodium tetrakis(p-fluorophenyl)borate;

PhBDMPT: tetraphenylboron dimethyl-p-toluidine salt;

PhBDMEM: tetraphenylboron dimethylaminoethyl methacrylate salt;

BFPhBNa: sodium butyltri(p-fluorophenyl)borate.

(6) Organic sulfinic acid salts, used as component (F)

PTSNa: sodium p-toluenesulfinate;

PTSLi: lithium p-toluenesulfinate;

BSNa: sodium benzenesulfinate.

(7) Organic solvents, used as component (I)

IPA: isopropyl alcohol.

Example 1

A dental adhesive composition of this invention comprising 5 wt parts ofMAC10, 75 wt parts of MMA and 20 wt parts of HEMA as component (A); 93wt parts of PMMA1 and 7 wt parts of PEMA1 as component (B); 3 wt partsof DMPT and 2 wt parts of BPO as component (C) was evaluated for aproper-viscosity reaching time, a working time, a curing time andadhesion performance as follows.

(1) Determination of a Proper-viscosity Reaching Time and a Working Time

To a mixing dish was added dropwise 0.103 g of a liquid compositionconsisting of 5 wt parts of MAC10, 75 wt parts of MMA, 20 wt parts ofHEMA and 3 wt parts of DMPT at 23° C. Then, to the mixture was added0.142 g of powders consisting of 93 wt parts of PMMA1, 7 wt parts ofPEMA1 and 2 wt parts of BPO, and the mixture was stirred with a stirringspatula for several seconds at intervals of about 5 sec. A time untilthe mixture could become to be taken with the spatula (properly viscousstate) was measured as a proper-viscosity reaching time. After theproper-viscosity reaching time, the mixture was further stirred and atime until the mixture began to adhere to the spatula as a thread wasmeasured. Thus, a working time was determined as a difference betweenthe latter time and the proper-viscosity reaching time.

(2) Method for Determining a Curing Time

An adhesive composition of this invention was prepared as described in(1). Immediately after reaching a properly viscous state, the mixturewas placed in a differential scanning calorimeter (DSC) at 37° C.Measurement was started and a time taken to give the maximum curing heatwas measured. A time from the start of measurement to the maximum curingheat was determined as a curing time.

(3) Method for Evaluating Adhesion Performance

Within 24 hours after slaughtering, a bovine front tooth was removed.While pouring water, the tooth was abraded along with a lip surface toexpose a dental enamel and a dentin. The exposed tooth surface was driedby blowing it with compressed air for about 10 sec. Then, on the surfacewas attached a double-stick tape having an opening with a diameter of 3mm, to form a simulated cavity. In the simulated cavity was applied aproper amount of a dental primer a prepared from 1.7 g of PM, 0.5 g ofUDMA, 0.1 g of PhBTEOA, 0.2 g of PTSNa, 4.2 g of acetone and 3.3 g ofwater. After standing for 30 sec, the applied surface was blown withcompressed air for about 5 sec. Then, in the simulated cavity wascharged the above dental adhesive composition of this invention in aproperly viscous state, on which was then attached a stainlessattachment with a diameter of 8 mm φ under pressure to prepare anadhesion test sample.

After immersing the adhesion sample in water at 37° C. for 24 hours, anadhesive strength between the tooth and the attachment was measuredusing a tensile tester (autograph, Shimadzu Corporation) at a crossheadspeed of 1 mm/min.

The measurement results were as follows; a proper-viscosity reachingtime: 20 sec, a working time: 100 sec, a curing time: 3.8 min, anadhesive strength to the dental enamel: 23.5 MPa, and an adhesivestrength to the dentin: 21.4 MPa, indicating that the dental adhesivecomposition of this invention exhibits good operability and improvedadhesion performance.

Examples 2 to 15

Dental adhesive compositions of this invention were prepared asdescribed in Example 1, except that those shown in Table 1 were used ascomponent (B), and their various properties were evaluated. The resultsare shown in Table 1, indicating that all of these dental adhesivecompositions exhibit good operability and improved adhesion performance.

TABLE 1 Non-crosslinking polymer Curing Tensile adhesive sphericalfiller(wt parts) Proper-viscosity Working time strength (MPa) PMMAspherical filler PEMA spherical filler reaching time(s) time(s) (min)Enamel Dentin Ex. 1 PMMA1(93) PEMA1(7) 20 100 3.8 23.5 21.4 Ex. 2PMMA2(95) PEMA1(5) 20 100 3.7 24.5 20.9 Ex. 3 PMMA3(93) PEMA1(7) 20 803.8 22.1 20.4 Ex. 4 PMMA4(90) PEMA2(10) 10 80 3.2 19 19.4 Ex. 5PMMA1(83) + PMMA2(10) PEMA1(7) 20 100 3.8 22.9 21.2 Ex. 6 PMMA1(48) +PMMA3(45) PEMA3(7) 20 110 3.9 20.4 21.6 Ex. 7 PMMA2(73) + PMMA4(20)PEMA1(7) 20 100 3.6 20.1 21.3 Ex. 8 PMMA1(80) + PMMA4(18) PEMA2(2) 30120 4.1 22.5 20.9 Ex. 9 PMMA1(70) + PMMA5(25) PEMA1(5) 20 110 3.6 21.420.6 Ex. 10 PMMA2(73) + PMMA5(20) PEMA1(7) 20 70 3.2 22.8 21.5 Ex. 11PMMA1(87) + PMMA6(10) PEMA1(3) 20 120 4 21.8 22 Ex. 12 PMMA1(35) +PMMA2(40) + PMMA3(20) PEMA1(5) 20 100 3.5 20.7 21.3 Ex. 13 PMMA1(43) +PMMA3(40) + PMMA4(10) PEMA2(7) 20 90 3.6 21.5 20.6 Ex. 14 PMMA1(20) +PMMA2(23) + PMMA5(50) PEMA1(7) 20 100 3.4 21.4 22.4 Ex. 15 PMMA1(43) +PMMA2(30) + PMMA6(20) PEMA1(3) + PEMA2(4) 20 100 3.7 22.3 19.9 Comp. Ex.1 PMMA1(100) — 120 100 5.7 21 19.9 Comp. Ex. 2 PMMA1(80) + PMMA3(20) —110 110 5.6 20.7 20.7 Comp. Ex. 3 — PEMA1(100) 0 10 2.6 18.9 15.3

Comparative Example 1

A dental adhesive composition was prepared as described in Example 1,substituting 100 wt parts of PMMA1 alone for component (B) as anon-crosslinking polymer filler, and its various properties wereevaluated. The results are shown in Table 1.

In this comparative example, a working time and an adhesive strengthwere as good as in Example 1, but a proper-viscosity reaching time and acuring time were increased, indicating inadequate operability.

Comparative Examples 2 and 3

Dental adhesive compositions were prepared as described in Example 1,using those shown in Table 1 as a non-crosslinking polymer filler, andits various properties were evaluated. The results are shown in Table 1.

Since a PEMA spherical filler was not used in Comparative Example 2, itis indicated that a proper-viscosity reaching time and a curing timewere increased, leading to inadequate operability, as is in ComparativeExample 1. In Comparative Example 3 in which a PEMA spherical filleralone was used, a working time was significantly reduced, leading toinadequate operability.

Example 16

A mixed liquid of component (A) consisting of 7.5 g of MMA, 0.5 g ofMAC-10 and 2.0 g of HEMA and 0.3 g of DMPT as component (C), and a mixedpowder of component (B) consisting of 4.6 g of PMMA1, 4.7 g of PMMA5 and0.7 g of PEMA1 and 0.2 g of BPO as component (C) were separatelyprepared. Immediately before use, the mixed liquid and the mixed powderwere kneaded at a powder/liquid ratio (wt/wt) of 1.4, to prepare adental adhesive composition of this invention. An adhesive strength wasdetermined as described in step (3) in Example 1, using the dentaladhesive composition thus prepared. The results were as follows; anadhesive strength to a dental enamel: 23.7 MPa, and an adhesive strengthto a dentin: 21.4 MPa. That is, a higher strength was observed for bothmaterials.

Examples 17 to 27

An adhesive strength was determined as described in Example 16,substituting different dental primers having the compositions shown inTable 2 for primer a, in which the primers used in Examples 17 to 27 arereferred to as primers b to 1, respectively. The results are shown inTable 2. As seen from Table 2, a higher adhesive strength was observedin all Examples.

TABLE 2 Primer composition(wt parts) (D) Acidic-group (E) (F) Organo-Tensile adhesive containing Aryl sulfinic (G) Water + (H) Other poly-strength(MPa) polyeriz-able monomer borate acid salt (I) Organic solventmerizable monomers Enamel Dentin Ex. 16 PM(17) PhBNa(1) PTSNa(2)Water(33) + Acetone(42) UDMA(5) 23.7 21.4 Ex. 17 PM(8) PhBNa(1) PTSNa(1)Water(60) HEMA(30) 18.5 17.9 Ex. 18 PM(5) PhBTEOA(0.1) PTSNa(1)Water(93.9) — 17.2 17.1 Ex. 19 PM(20) PhBNa(1) BSNa(1) Water(40) +Acetone(35) TMPT(3) 25.4 19.7 Ex. 20 PM(20) PhBNa(1) PTSNa(1)Water(33) + Acetone(36) + IPA(4) UDMA(5) 23.7 22.7 Ex. 21 MAC-10(5) +PM(15) PhBTEOA(1) PTSNa(3) Water(36) + D-2.6E(5) 21.1 18.9 Acetone(25) +IPA(10) Ex. 22 MAC-10(10) + PM(10) FPhBNa(3) BSNa(5) Water(35) +Acetone(27) UDMA(10) 20.8 21.5 Ex. 23 4-META(10) + PM(10) PhBDPT(5)PTSLi(1) Water(41) + Acetone(23) UDMA(5) + 23.6 19.8 D-2.6E(5) Ex. 24MAC-10(10) + PM(15) PhBDMEM(2) PTSNa(0.3) Water(25) + Acetone(42.7)Bis-GMA(3) + 3G(2) 22.6 19.3 Ex. 25 PM(20) BFPhBNa(0.5) PTSNa(1) +Water(39.5) + Acetone(20) UDMA(5) + HMA(5) 24.6 18.9 BSNa(1) Ex. 26PM(20) PhBNa(1) PTSNa(2) Water(37) + Acetone(35) UDMA(3) + 3G(2) 22.220.5 Ex. 27 4-META(10) + PhBNa(1) + PTSNa(1) Water(37) + Acetone(35)UDMA(3) + TMPT(2) 18.3 21.4 MAC-10(10) PhBTEOA(1) Comp. Ex. 4 — PhBNa(1)PTSNa(1) Water(48) + Acetone(45) UDMA(5) 0.6 3.6 Comp. Ex. 5 PM(20) —PTSNa(1) Water(39) + Acetone(35) UDMA(5) 15.4 12.1 Comp. Ex. 6 PM(20)PhBNa(1) — Water(39) + Acetone(35) UDMA(5) 16.4 13.4 Comp. Ex. 7 PM(20)PhBNa(1) PTSNa(1) — UDMA(78) — —

Comparative Examples 4 to 7

An adhesive strength was determined as described in Example 16, usingdifferent dental primers having the compositions shown in Table 2, inwhich the primers used in Comparative Examples 4 to 7 are referred to asprimers m to p, respectively. The results are shown in Table 2.

In Comparative Example 4, in which an acidic-group containingpolymerizable monomer was not contained in the primer, adhesive strengthvalues to a dental enamel and a dentin were as low as 0.6 MPa and 3.6MPa, respectively. In Comparative Example 5, in which an aryl borate wasnot contained in the primer, an adhesive strength to a dentin wassignificantly lowered. In Comparative Example 6 without anorganosulfinic acid salt, an adhesive strength to a dentin wassignificantly lowered. In Comparative Example 7 without water or asolvent, a homogeneous solution failed to be prepared because PTSNa asan organosulfinic acid salt was not dissolved in PM and UDMA and theprimer failed to exhibit a proper viscosity. Thus, an adhesion testcould not be conducted.

Example 28

A mixed liquid of component (A) consisting of 7.5 g of MMA, 0.5 g ofMAC-10 and 2.0 g of HEMA and 0.3 g of DMPT as component (C), and a mixedpowder of component (B) consisting of 9.3 g of PMMA1 and 0.7 g of PMMA1and 0.2 g of BPO were separately prepared. Immediately before use, themixed liquid and the mixed powder were kneaded at a powder/liquid ratioof 1.4, to prepare a dental adhesive composition. An adhesive strengthwas determined as described in Example 16, using the dental adhesivecomposition thus prepared and the primer a used in Example 16. Theresults were as follows; an adhesive strength to a dental enamel: 23.4MPa, and an adhesive strength to a dentin: 22.1 MPa. That is, a higheradhesive strength was observed.

Examples 29 to 51

An adhesive strength was determined as described in Example 16, usingdifferent dental primers of this invention having the compositions shownin Tables 3 and 4, and different primers (primers a, e and k). However,when adding a photopolymerization initiator to component (C), further anattachment was welded under a pressure and then irradiation wasconducted from four directions around the attachment for 30 sec for eachdirection. The results are shown in Tables 3 and 4. In all Examples,higher adhesive strength was observed to both dental enamel and dentin.

TABLE 3 Composition of dental adhesive compositions(wt parts)Polymerizable monomer comprising an acidic-group containignploymerizable monomer Acidic group Non-crosslinking containing sphericalfiller polymerizable Other monomer polymerizable monomers PMMAPolymeriza- Tensile adhesive Pri- P MA 4-ME M HEM D-26 Bis-G UD PMMAspherical tion initiator strength(MPa) mer M C-10 TA MA A E TMPT MA 3GMA spherical filler filler BPO DMPT Enamel Dentin Ex. a — 5 — 75 20 — —— — — PMMA1(130.2) PEMA1(9.8) 2.8 3 23.4 22.1 28 Ex. a — 5 — 75 20 — — —— — PMMA1(102.2) + PEMA1(9.8) 2.45 3 23.1 21.8 29 PMMA2(28) Ex. a — — 575 20 — — — — — PMMA1(105) + PEMA1(7) 2.8 3 24.5 20.8 30 PMMA3(28) Ex. a5 — — 75 20 — — — — — PMMA1(120.2) + PEMA1(9.8) 2.1 3 20.7 19.9 31PMMA4(10) Ex. e — 3 — 77 20 — — — — — PMMA2(105) + PEMA1(7) 2.8 3 21.119.7 32 PMMA3(28) Ex. e — 10 — 70 20 — — — — — PMMA1(116.2) + PEMA1(9.8)2.8 5 22.2 19.7 33 PMMA5(14) Ex. e — 20 — 70 10 — — — — — PMMA1(112) +PEMA1(4.2) 2.8 3 20.8 17.9 34 PMMA5(23.8) Ex. e 5 5 — 60 20 10 — — — —PMMA4(70) + PEMA1(7) 2.1 3 21.4 20.4 35 PMMA5(63) Ex. k — 5 5 65 20 — 5— — — PMMA1(105) + PEMA2(7) 1.4 2 22.3 21.1 36 PMMA3(28) Ex. k — 5 — 7015 — — 6 4 — PMMA1(70.2) + PEMA2(9.8) 2.8 3 21.6 20.6 37 PMMA5(60) Ex. k— 5 — 65 20 — — — — 10 PMMA2(105) + PEMA3(7) 2.45 3 21 19.8 38 PMMA3(28)Ex. k — 10 — 65 15 10 — — — — PMMA3(109.2) + PEMA3(2.8) 2.1 3 20.8 20.539 PMMA(28)

TABLE 4 Composition of dental adhesive compositions(wt parts)Polymerizable monomer comprising an acidic-group containingpolymerizable monomer Acidic group Non-crosslinking containing Otherspherical filler polymerizable polymerizable monomer monomers PEMAPolymerization initiator Tensile adhesive Pri- MA 4-ME M HE D-2 TM PMMAspherical DM DM PhB strength(MPa) mer C-10 TA MA MA .6E PT sphericalfiller filler BPO PT CQ BE Na Enamel Dentin Ex. 40 a 5 — 75 20 — —PMMA1(105.2) + PEMA1(9.8) 2.8 3 2 2 — 24.7 23.4 PMMA2(25) Ex. 41 a 5 —75 20 — — PMMA3(70.2) + PEMA1(9.8) 2.8 3 — — 2 23.1 22.2 PMMA4(60) Ex.42 a 5 — 75 20 — — PMMA1(105) + PEMA1(7) 2.8 3 2 2 1 24 20.8 PMMA5(28)Ex. 43 a 5 5 70 20 — — PMMA3(112) + PEMA1(2.8) 2.1 3 — — — 24 22.7PMMA5(25.2) Ex. 44 e 5 — 65 20 10 — PMMA1(52) + PEMA1(7) 2.8 3 — — —25.1 22.5 PMMA2(52) + PMMA3(29) Ex. 45 e 10 — 65 15 10 — PMMA1(50) +PEMA2(9.8) 2.8 3 2 2 — 21.6 23 PMMA3(50) + PMMA5(30.2) Ex. 46 e 5 — 7515 — 5 PMMA1(50) + PEMA1(7) 2.8 3 — — 1 21 22.4 PMMA3(50) + PMMA4(33)Ex. 47 e — 5 70 20 — 5 PMMA1(60.2) + PEMA2(9.8) 2.1 3 — — — 21.1 23.5PMMA3(42) + PMMA6(28) Ex. 48 k 5 — 75 20 — — PMMA1(32) + PEMA1(7) 2.45 2— — — 20.8 21.9 PMMA2(32) + PMMA5(69) Ex. 49 k 5 — 75 20 — — PMMA1(30) +PEMA1(9.8) 2.8 2 — — — 23.1 22.7 PMMA2(30) + PMMA6(70.2) Ex. 50 k 10 —70 20 — — PMMA1(105) + PEMA1(4) + 2.45 3 — — 1 21.5 22.5 PMMA3(28)PEMA2(3) Ex. 51 k 5 — 75 10 10 — PMMA1(50) + PEMA1(4) + 2.45 3 — — —21.9 23.5 PMMA3(50) + PEMA3(3) PMMA5(33) Comp. a — — — — — —PMMA1(105) + PEMA1(7) 2.8 3 — — — — — Ex. 8 PMMA2(28) Comp. a — — 70 2010 — PMMA1(105) + PEMA1(7) 2.8 3 — — — 0.5 3.4 Ex. 9 PMMA3(28) Comp. e 5— 65 20 10 — — — 2.8 3 — — — — — Ex. 10 Comp. e 5 — 65 20 10 —PMMA1(105) + PEMA1(7) — — — — — — — Ex. 11 PMMA3(28)

Comparative Examples 8 to 11

An adhesive strength was determined as described in Examples 29 to 51,using dental adhesive compositions having the compositions and theprimers shown in Table 4. The results are shown in Table 4.

Comparative Example 8 is an example which is without an acidic-groupcontaining polymerizable monomers or other polymerizable monomers ascomponent (A) in an adhesive composition, an adhesion test could not beconducted.

Comparative Example 9 is an example which is without an acidic-groupcontaining polymerizable monomer in an adhesive composition, adhesivestrength to a dental enamel and dentin was significantly lowered.Comparative Example 10 is an example which is without a non-crosslinkingpolymer filler in an adhesive composition, the composition did not havea proper viscosity so that an adhesion test could not be conducted.Comparative Example 11 is an example which is without a polymerizationcatalyst, the composition failed to be polymerized so that an adhesiontest could not be conducted.

What is claimed is:
 1. A dental adhesive composition comprising (A) apolymerizable monomer comprising an acidic-group containingpolymerizable monomer; (B) a spherical filler substantially consistingof a non-crosslinking polymethyl methacrylate and a spherical fillersubstantially consisting of a non-crosslinking polyethyl methacrylate;and (C) a polymerization initiator.
 2. The dental adhesive compositionas claimed in claim 1 wherein a content of (A) the polymerizable monomercomprising an acidic-group containing polymerizable monomer is 25 to 65wt parts to 100 parts of the total amount of (A) the polymerizablemonomer comprising an acidic-group containing polymerizable monomer, (B)the spherical filler substantially consisting of a non-crosslinkingpolymethyl methacrylate and the spherical filler substantiallyconsisting of a non-crosslinking polyethyl methacrylate and (C) thepolymerization initiator; a content of (B) the spherical fillersubstantially consisting of a non-crosslinking polymethyl methacrylateand the spherical filler substantially consisting of a non-crosslinkingpolyethyl methacrylate is 35 to 70 wt parts to 100 parts of the totalamount of (A) the polymerizable monomer comprising an acidic-groupcontaining polymerizable monomer, (B) the spherical filler substantiallyconsisting of a non-crosslinking polymethyl methacrylate and thespherical filler substantially consisting of a non-crosslinkingpolyethyl methacrylate and (C) the polymerization initiator; a contentof (C) the polymerization initiator is 0.01 to 20 wt parts to 100 partsof (A) the polymerizable monomer comprising an acidic-group containingpolymerizable monomer.
 3. The dental adhesive composition as claimed inclaim 1 wherein a content of the acidic-group containing polymerizablemonomer is 3 to 70 wt parts of (A) the polymerizable monomer comprisingthe acidic-group containing polymerizable monomer.
 4. The dentaladhesive composition as claimed in claim 1 wherein (A) the polymerizablemonomer comprising an acidic-group containing polymerizable monomercomprises 11-methacryloyloxy-1,1-undecane dicarboxylic acid.
 5. Thedental adhesive composition as claimed in claim 1 wherein (A) thepolymerizable monomer comprising an acidic-group containingpolymerizable monomer comprises a polymerizable monomer having afunctional group including a thiouracil, triazinethione ormercaptothiazole derivative at 0.1 to 50 wt parts to 100 wt parts of (A)the polymerizable monomer comprising an acidic-group containingpolymerizable monomer.
 6. The dental adhesive composition as claimed inclaim 1 wherein an average particle size of (B) the spherical fillersubstantially consisting of a non-crosslinking polymethyl methacrylateand the spherical filler substantially consisting of a non-crosslinkingpolyethyl methacrylate is 0.1 to 50 μm.
 7. The dental adhesivecomposition as claimed in claim 1 wherein the spherical fillersubstantially consisting of a non-crosslinking polymethyl methacrylatein (B) is a mixture of a spherical filler having a weight averagemolecular weight of less than 100,000 and a spherical filler having aweight average molecular weight of 100,000 or more.
 8. A dental adhesionkit comprising the dental adhesive composition as claimed in claim 1 incombination with a dental primer comprising (D) an acidic-groupcontaining polymerizable monomer, (E) an aryl borate, (F) anorganosulfinic acid salt and (G) water.
 9. The dental adhesion kit asclaimed in claim 8 wherein a content of (D) the acidic-group containingpolymerizable monomer in the primer is 1 to 50 wt parts to 100 parts ofthe total of the components of the primer; a content of (E) the arylborate is 0.01 to 25 wt parts to 100 parts of the total of polymerizablemonomer of the primer; a content of (F) the organosulfinic acid salt is0.01 to 25 wt parts to 100 parts of the total of polymerizable monomerof the primer; and a content of (G) water is 5 to 95 wt parts to 100parts of the total of the components of the primer.
 10. The dentaladhesion kit as claimed in claim 8 wherein (E) the aryl borate has threeor four aryl groups in one molecule.
 11. A dental adhesion kitcomprising the dental adhesive composition as claimed in claim 1 incombination with a dental primer comprising (D) an acidic-groupcontaining polymerizable monomer, (E) an aryl borate, (F) anorganosulfinic acid salt, (G) water, (H) a polymerizable monomer otherthan the acidic-group containing polymerizable monomer and (I) anorganic solvent.